By Jeffrey S Graybill, Agronomy Extension Educator
With the increased use of diverse cover crop species, some farmers are finding that winter injury and winterkill can become a problem.
Traditionally, when we think of winterkill, we assume that a very cold snap combined with factors such as wet soils and frost heaving are the culprits. This is generally true for late-planted covers that have not developed an adequate root system nor carbohydrate reserves. Physical injury, cold temperatures and desiccation combine to stress and potentially kill tender young plants.
However, with the advent of a warm fall and extended growing season, we are seeing the opposite. Species with excellent growth and establishment go into winter looking great and when the snow melts large areas of foliage have “smothered” and died. In many cases the growing points are also affected and the areas are either very slow to green up or are entirely dead.
Snow mold is often the main culprit. A thick lush canopy of leaves will hold moisture and prevent air circulation and sunlight from entering the canopy. This provides an ideal environment for the various diseases collectively called snow molds. Leaves in contact with the soil are often affected first.
Snow cover coupled with temperatures just above freezing in the canopy will allow the disease to continue infecting upper leaves and with prolonged periods kill the crown. Snow molds primarily affect grasses, but I have also seen winterkill in crimson clover and other non-grass species.
Here in south central Pennsylvania, annual ryegrass seems to be particularly sensitive, with barley, wheat and cereal rye less so. What’s the solution? Ryegrass has excellent yield and nutritional factors, so I don’t want to discourage you from growing it. One consideration is to include ryegrass as part of a mixture with other grasses and legume species. I have grown a ryegrass, triticale and crimson clover mixture for the past 3 successive years here in Lancaster County with excellent results.
Another option is to monitor growth, and if needed, take a late cutting to open up the canopy and remove excessive biomass. It’s not too late to walk your ryegrass plantings and consider this option. If the canopy is approaching 7-8 inches and is fairly thick, a cutting may be warranted.
Small grains, such as wheat, barley and rye, should not be as susceptible until they are 10-12 inches tall. However, if soil warmth and plant growth continues into the end of November even these fields may be “set up” for significant winter injury. In both cases, the excessive growth could be harvested for forage provided the volume is sufficient, or left on the field if uniformly scattered.
If you have excessive biomass but cannot remove or uniformly scatter the forage, it may be better to do nothing. Another option for some growers would be to graze these fields when soil conditions permit. Taking a high cutting about 4-5 inches is a consensus I’ve found amongst the local seed industry.
Finally, environmental conditions from here on out will have a great effect on winter injury this year and every year.